Gearbox lubrication system

ABSTRACT

A high speed gearbox includes a housing which encloses a rotating gear and a volume which contains oil and air. The gear has an outer first surface exposed to the volume and has a second surface exposed to the environment. A vent arrangement includes first and second passages formed in the gear. The second passage extends axially part way into the gear and has an outer end exposed to the second surface. The first passage extends radially from the first surface to the second passage. A check valve is mounted in the second passage and permits one-way flow of air from the volume to the environment.

FIELD

The present disclosure relates to a lubrication system for a gearbox.

BACKGROUND

Vehicle transmissions, such as power take off (PTO) transmissions, have shafts and gears which rotate in a housing which forms an oil sump so that the parts are adequately coated with lubricating oil while they rotate. Certain PTO transmissions have a pressurized lube system wherein sump oil level which is above the center of a shaft, and radial passages in the shaft pull oil through the shaft. Shaft and gear rotation causes the sump oil to be thrown away from the center of the transmission.

Lube fluid for a transmission can also be diverted from a tractor hydraulic system. But, this requires balancing lube systems, returning and controlling sump oil levels, and mixing oil with a gear box that is coupled to an implement, such as a planter. A transmission lubrication system can also include a small lube pump. However, this increases costs due to the additional parts, such as screens, lines and cooling requirements.

In a known small gear box, a needle bearing is sandwiched between two gears which rotate at lower and higher speeds, respectively. The gear box does not have any pressurized lube system or lube pump and will only use sump oil splash for cooling and lubrication. Due to the rotation of the gears, centripetal force will push sump oil away from the needle bearing and an adjacent ball bearing. It is desired to have a system which delivers lubrication oil to the bearings while working against the centrifugal force created by the rotating gears.

SUMMARY

According to an aspect of the present disclosure, a gearbox has a housing which encloses a rotating gear and a volume which contains oil and pressurized air. The gear has a first surface exposed to the volume and a second surface exposed to the environment. A vent arrangement includes first and second passages formed in the gear. The second passage extends part way into the gear and has an outer end exposed to the second surface. The first passage extends radially outwardly from the second passage to the first surface. The second passage extends axially along a central axis of the gear. A check valve is mounted in the second passage and permits one-way flow of air from the volume to the environment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a gearbox which embodies the present invention;

FIG. 2 is an exploded sectional perspective view of a gearbox which embodies the present invention;

FIG. 3 is a sectional view along lines 3-3 of FIG. 1; and

FIG. 4 is a perspective view of the input gear of the gearbox of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIGS. 1, 2 and 3, a rotary machine such as a gearbox 10, such as for a power take off (PTO), includes an outer housing 12 which includes bolted together housing parts 11 and 13. Housing 12 surrounds rotating parts including an input gear 14. Input gear drives a drive gear 16, which, in turn drives an output gear 18 at a high speed, such as 1000 rpm. Input gear 14 includes a larger diameter flange 20 and a smaller diameter hub 22. A hollow needle bearing 24 is mounted on the hub 22, and the bearing 24 rotationally supports the output gear 18. As best seen in FIGS. 2 and 3, a conventional ball bearing 26 supports the output gear 18 for rotation in the housing part 11. A snap ring 28 retains the needle bearing 24 in position inside the output gear 18. An annular washer 30 is mounted next to the input gear 14. With respect to FIGS. 1, 2 and 4, the input gear 14 rotates in a clockwise direction.

Referring to FIGS. 3 and 4, the flange 20 of the input gear 14 has a larger diameter axially thinner flange portion 29 and a smaller diameter axially thicker flange portion 31. Flange portion 29 forms an outer annular axially facing surface 33. Flange portion 31 forms an inner annular axially facing surface 34. Inner surface 33 is positioned radially inwardly from outer surface 34. Inner surface 33 is spaced axially apart from outer surface 34 in a direction towards output gear 18. The washer 30 engages and covers surface 33 of thicker flange portion 31.

A radially outwardly facing peripheral wall or annular surface 35 extends between surfaces 34 and 33, and surrounds the smaller diameter flange portion 31. An inner portion of smaller diameter flange portion 31 forms an annular rim 36 which projects generally axially from surface 34. An annular channel 38 is formed between the rim 36 and an axially inner end 32 of the hub 22. Annular peripheral surface 35 has a diameter which is larger than a diameter of the hub 22.

A plurality (preferably two) milled slots or grooves 40 and 42 extend radially inwardly from the wall 35, through smaller diameter flange portion 31, through the rim 36 and to the channel 38. The slots 40 and 42 may be curved or spiral shaped. Thus, the grooves 40 and 42 communicate the outer edge of smaller diameter flange portion 31 with the outer surface of hub 22. The outer ends of the groves 40 and 42 are forward of their inner ends with respect to the direction of rotation of the input gear 14. Thus, the slots 40 and 42 in the side of the input gear 14 scoop sump oil and direct it inwardly through the slots 40 and 42 towards the needle bearing 24.

Referring again to FIG. 3, the output gear 18 forms an inner cavity 50 which receives the hub 22 and the needle bearing 24. The output gear 18 also forms an outer cavity 52 which has inner splines 54 and is adapted to receive a PTO shaft (not shown). The output gear 18 also includes a passage 56 which communicates the inner cavity 50 to an outer peripheral surface of the output gear adjacent to the bearing 26.

The passage 56 in the output gear 18, which rotates at 6000 rpm, creates an under-pressure that helps pull oil through the needle bearing 24 and communicate oil to the ball bearing 26. Because of the differential in speed between the input gear 14 and the output gear 18, the passage 56 in output gear 18 will create more of an under-pressure than the slots 40 and 42 in the slower rotating (1000 rpm) input gear 14.

Thus, as the input gear 14 rotates, the spiral grooves 40 and 42 scoop lubrication oil from the interior of the housing 12 and impel this oil radially inwardly though the rim 36 and onto the outer surface of the hub 22. A pressure differential pulls this oil through the needle bearing 24, then through the passage 56 and through the bearing 26. The result is a system which using the rotation of the gears to create a pressure differential which sends lubricating sump oil to a buried needle bearing and ball bearing. Without these features, sump oil would normally be thrown outwardly and away from the centrally located bearings 24 and 26.

While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. It will be noted that alternative embodiments of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the present invention as defined by the appended claims. 

What is claimed is:
 1. A rotary machine lubrication assembly, comprising: a housing enclosing a volume which contains oil; a first part mounted for rotation in the housing, the first part having a central hub and a flange which projects outwardly from the hub; an annular bearing is mounted on the hub; a second part mounted on the bearing for rotation in the housing; and a first passage formed in the first part, the first passage directing oil from the volume to a peripheral surface of the hub and to the bearing upon rotation of the first part.
 2. The rotary machine lubrication assembly of claim 1, further comprising: a further bearing rotatably supporting the second part with respect to the housing; and a second passage in the second part, the second passage communicating oil from the annular bearing to the further bearing.
 3. The rotary machine lubrication assembly of claim 2, wherein: the second part includes a sleeve which surrounds a cavity which receives the first bearing; and the second passage extends axially and radially outwardly from the cavity to an outer surface of the second part.
 4. The rotary machine lubrication assembly of claim 1, wherein: the first passage has a radially outer end and a radially inner end, the outer end being forward of the inner end with respect to a rotation direction of the first part.
 5. The rotary machine lubrication assembly of claim 1, wherein: the first part includes a larger diameter flange portion and a smaller diameter flange portion, the smaller diameter flange portion being surrounded by a peripheral surface, the first part also including an annular rim which surrounds the hub; an annular channel is formed between the rim and the hub; and the first passage comprises a slot which extends through the smaller diameter flange portion and through the rim, and communicates the peripheral surface with the channel and an outer surface of the hub.
 6. The rotary machine lubrication assembly of claim 5, wherein: the larger diameter flange portion forms an annular axially facing outer surface, the smaller diameter flange portion forms an annular axially facing inner surface, and the inner surface 33 is spaced axially apart from outer surface 34 in a direction towards output gear
 18. 7. The rotary machine lubrication assembly of claim 5, wherein: an annular washer 30 engages and covers a surface 33 of smaller diameter flange portion
 31. 8. The rotary machine lubrication assembly of claim 1, wherein: the first part includes a larger diameter axially thinner flange portion and a smaller diameter axially thicker flange portion, the smaller diameter flange portion being surrounded by a peripheral surface, the first part also including an annular rim which surrounds the hub; an annular channel is formed between the rim and the hub; and the first passage comprises a slot which extends through the smaller diameter flange portion and through the rim, and communicates the peripheral surface with the channel and an outer surface of the hub.
 9. The rotary machine lubrication assembly of claim 8, wherein: the larger diameter flange portion forms an annular axially facing outer surface, the smaller diameter flange portion forms an annular axially facing inner surface, and the inner surface 33 is spaced axially apart from outer surface 34 in a direction towards output gear
 18. 10. The rotary machine lubrication assembly of claim 8, wherein: an annular washer 30 engages and covers a surface 33 of the axially thicker flange portion
 31. 11. The rotary machine lubrication assembly of claim 1, wherein: the first part is an input gear of a gearbox; and the second part is an output gear of the gearbox, the output gear rotating faster that the input gear.
 12. A rotary machine lubrication assembly, comprising: a housing enclosing a volume which contains oil; a first part mounted for rotation in the housing, the first part having a central hub and a flange which projects outwardly from the hub; a second part mounted for rotation in the housing, the second part having a sleeve which receives a portion of the hub; and a first annular bearing which is mounted on the hub and which is received by the sleeve; a second bearing rotatably supporting the second part with respect to the housing; a first passage formed in the first part, the first passage directing oil from the volume to a peripheral surface of the hub and to the first bearing upon rotation of the first part; and a second passage in the second part, the second passage communicating oil from the annular bearing to the further bearing.
 13. The rotary machine lubrication assembly of claim 12, wherein: the flange includes a larger diameter axially thinner flange portion and a smaller diameter axially thicker flange portion, the smaller diameter flange portion being surrounded by a peripheral surface; and the first passage comprises a slot formed in a surface of the smaller diameter flange portion.
 14. The rotary machine lubrication assembly of claim 13, wherein: the first part also includes an annular rim which surrounds the hub; an annular channel is formed between the rim and the hub; and the slot extends through the smaller diameter flange portion and through the rim, and communicates the peripheral surface with the channel and with an outer surface of the hub.
 15. A rotary machine lubrication assembly, comprising: a housing enclosing a volume which contains lubricating fluid; a part mounted for rotation in the housing, the part having a central hub and a flange which projects radially outwardly from the hub, a portion of the flange forming an annular peripheral surface having a diameter which is larger than a diameter of the hub; an annular bearing which is mounted on the hub; and a passage formed in a surface of the part, the passage directing lubricating fluid from the volume to an outer surface of the hub and to the bearing upon rotation of the part.
 16. The rotary machine lubrication assembly of claim 15, wherein: the part includes a rim which surrounds a base of the hub; an annular groove is formed between the rim and the hub, and the passage extends radially inwardly from the peripheral surface through the rim and into the groove. 